Hi,
I did initially consider renewing my PPL with them as i was initially taught by Mark back in 07 - 10 when he was at St Georges ( cant speak highly enough of him as an instructor). I managed to get 1 flight in before being lucky enough to get another some 6+ weeks later which was cancelled due to A/C serviceability, attempts to book in for more proved chaotic as mentioned above by Shango.
If your set on learning to fly at Teesside and why wouldn't you the North East is the greatest place on earth! check out Scenic Air Tours, after giving up with Eden I moved to them and renewed my PPL within 3 Months (flying only at weekends), and have since started my Hour Building and Night Rating with them with plans to start the IRR soon.
They have a fleet of 3 x PA28 at £180 Ph (slightly more than Eden) but.. aside from weather I have never had a booking cancelled due to instructor availability or aircraft serviceability so don't mind paying slightly more. and providing you plan in advance weekend availability isn't much of a problem, this is when they are busiest.
Hope this helps in your decision making
Chris